Fusible temperature responsive trigger device

ABSTRACT

A temperature responsive device having an extensible indicator rod or staff which is held in place within a bored shell by a quantity of solidified fusible material received within a chamber communicating with complemental surfaces formed on the inner axial end of the staff and the bottom of the bored shell.

United States Patent Jeffers 1451 Aug. 8, 1972 [s41 FUSlBLE TEMPERATURE 1,916,989 1/1933 Rader ..285/305 RESPONSIVE TRIGGER DEVICE 3,090,235 5/1963 Houser ..73/3S8 Inventor: D. letters, Fresno, 3,140,61 1 7/1964 KllWCI [73] Assignee: Jeffers & Bailey, Inc., Fresno, Calif. primary m i R p i 2 Filed; March 19, 9 Assistant Examiner-Denis E. Corr Attorney-James M. Naylor, Frank A. Neal and John [21] Appl. No: 441,199 Wilkinson 52 US. Cl ..ll6/ll4.5, 73/358, 99/192 'IT AB [51] Int. Cl. ..G0lk 11/06 A tem perature responsive device having an extensible [58] Field of Search.. ..99/19 2 T1, 116/ 1 14.5, 73/353, indicator rod or staff which is held in place within a 151/145 85/66 285/287 305 bored shell by a quantity of solidified fusible material [56] R f Cted received within a chamber communicating with come erences l plemental surfaces formed on the inner axial end of UNITED STATES PATENTS the staff and the bottom of the bored shell.

945,978 1/1910 Nielsen et a1 ..73/358 I 4 Claim, 6 Drawing Figures P'A'TENTEflAus a ma SHEEI 18F 2 26 I My 4' g y FIG. 2

I NVENTOR. WILLIAM 0. JEFFERS PATENTEM 8 m2 3.682.130

SHEET 2 BF 2 INVENT WILLIAM D. JEFFERS W M m FIGS m k q 7 FIG.

ATTORNEYS FUSIBLE TEMPERATURE RESPONSIVE TRIGGER DEVICE This invention relates to a temperature-responsive triggering device wherein a fusible metal locking body retains. two relatively moveable parts of the device in fixed relation against a biasing force until a preselected temperature is attained.

Of the many applications of the present invention, a temperature indicating device for apprising a chef of the cooked condition of viands, as disclosed in my copending application Ser. No. 352,391 and in U. S. Pat. No. 3,140,611, is cited here byway of example. A myriad of uses for the invention will occur to those skilled in the art, for example, in fire alarm systems and the like.

Prior art temperature-responsive devices employing a fusible alloy with which I am familiar require installation of a new fusible link or body when the device is reset after having been subjected to a temperature in excess of the yield temperature of the fusible alloy. Such replacement is not only expensive but is also troublesome in that such fusible metal bodies or links are frequentlyof very small size and mounted in virtually inaccessible portions of devices of the type here under discussion. Another disadvantage in such prior art devices is that the fusible metal is under constant stress, usually as a result of spring tension or like biasing element, and is subject to false indications resulting from fatigue of the fusible metal body. Attempts to strengthen the fusible link or locking body by enlarging it adversely affects the temperature sensitivity of the device; enlargement is impossible in compact devices such as those used in preparing viands.

For illustration, the present invention is hereinafter described in connection with a temperature-responsive device of the type described more fully in the U. S. Pat. 3,140,61 1 wherein an outer shell having a pointed end is provided and which shell is inserted into a fowl, roast, or like viand prior to placement into an oven. Such shell is bored to slidably receive a staff therein, a spring being provided for biasing the staff outwardly of the bore. A fusible locking body is provided within the bore for retaining the staff therein and against the force of the spring until a preselected temperature has been reached within the viand. Specific exemplary roasting conditions are disclosed in my copending patent application cited above. When a preselected temperature occurs adjacent the fusible element, the latter yields and permits the spring to move the staff outwardly of the shell, thereby providing a visual indication of the arrival of the preselected temperature. Although the prior art fusible links or bodies have been generally successful, the structure of the present invention provides a marked improvement. 1

In the present invention, the bottom of the bore and the inner end of the staff are formed with complementary surfaces so that when the staff is urged inwardly of the bore virtually no space exists between the longitudinal ends of the staff and bore. Adjacent the complementary portions, the staff and the bore are each formed with a mutually confronting annular depression or groove. Consequently, when a body of fusible metal is placed in the bore and is heated to a molten state, movement of the staff into the bore forces the molten metal out of the space between the staff and bore and into the generally torroidal chamber formed by the two annular depressions. The staff is there retained until the fusible metal is solidified by cooling at which point a secure, temperature-sensitive lock is afforded between the staff and the shell.

A feature and advantage of the present invention is that substantially all of the fusible metal contributes to withstanding the biasing force tending to move the staff relative to the bore. Accordingly, the unit stress on the material is reduced as a consequence of which false indications are eliminated and the amount of fusible metal needed is minimized.

A further feature and advantage of the device of this invention is that after the device triggers at the preselected temperature, the device can be reset merely by urging the staff inwardly of the bore and reducing the ambient temperature below the temperature of fusion of the fusible metal. By way of contrast, attention is respectfully invited to the patent cited hereinabove wherein a transversely extending pin has ends protruding for locking the staff in fixed relation to the bore and wherein on attainment of the yield temperature the ends of the pins are sheared off. Such prior art device can be reset only by disassembly and insertion of a new fusible pin.

Another feature and advantage of this invention resides in forming the annular groove in the sleeve bore with an outwardly converging surface portion so that the force imparted to the fusible body by the spring or like biasing means tends to lock the staff in the bore more firmly. Such outwardly converging wall portion imparts to the fusible body a torsional moment which distributes shear stresses throughout the fusible body rather than along a cylindric plane of the boundary between the staff and the shell bore. Accordingly, false temperature indications are further reduced or eliminated.

Still another feature and advantage of the present invention arises from a modification of the device wherein the staff is provided with a ridge on the surface thereof for entry into the annular depression in the sleeve bore. Such modified staff further includes at least one diametrally extending slot into which fusible metal is forced to urge the ridge into engagement with annular depression in the sleeve bore. The inner end of the staff and bore are formed with complementary surfaces so that on urging the staff inwardly of the bore when the metal is at the temperature of fusion, the molten metal will be forced into the slot and there retained after cooling to a temperature below the temperature fusion of the metal. When the temperature is again raised to the fusion temperatures of fusible metal, the stafi is freed to outward movement in response to the spring bias.

The foregoing as well as other objects, features and advantages will be more apparent after referring to the following specification and accompanying drawings in which:

FIG. 1 is a cross-sectional view of a temperatureresponsive device embodying the present invention;

FIG. 2 is an enlarged detailed view of a portion of FIG. 1;

FIG. 3 is a view similar to FIG. 2 wherein the temperature-responsive trigger is in locked condition;

FIG. 4 is a detailed view of a modification of the present invention;

the shell. A fusible alloy locking structure of the present invention is provided for retaining staff 16 within bore 14 against the force of spring 18 until a preselected temperature causes the fusible metal locking device to yield.

The locking device of the embodiment of FIGS. 1-3 includes a concave surface portion 20 at the bottom of bore 14 and a convex surface portion 22 on the longitudinal end of staff 16. Convex portion 22 and concave portion 20 are complementary with one another by which is meant that the convex portion will nest into or fit into the concave portion with substantial surface contact throughout the entire portion of the respective complementary surfaces.

In the specific example shown in the drawings, surface portions 20 and 22 are generally hemispheroidal. Rimming the outer portion of concave surface portion 20 is an annular depression or groove 24. Staff 16 adjacent convex portion 22 is formed with an annular depression or groove 26 that confronts annular depression or groove 24 when surface portion 22 is in engagement with concave surface portion 20 to define a generally torroidal chamber. Such relationship can be seen most clearly in FIG. 3. A quantity of fusible alloy 28 sufficient to fill the torroidal chamber to form a ring is provided in bottom 20 of bore 14. The constitution of such alloys is well-known by those skilled in the art; specific examples are given in my above cited co-pending application. Although in FIG. 2 fusible alloy 28 is shown as a sphere, such configuration is for convenience of description only and is merely anintermediate stage in the assembly of the present invention.

Operation of my improved temperature-responsive locking mechanism can be understood by assuming that the temperature of the structure is raised to a level above the fusion temperature of fusible alloy 28. In relatively low temperature applications this can be done by submersing the entire tip of the structure in boiling water. When the fusible alloy has melted and reached the fluid state, axial movement of staff 16 toward the bottom of bore 14 causes convex surface portion 22 of the staff to nest into the complementary concave surface portion 20 of the bore, and forces the molten alloy out of the space therebetween and into the torroidal chamber defined by annular depressions 24 and 26. Cooling of the structure and consequent solidification of the fusible alloy locks staff 16 in sleeve 12 against the force of spring 18. Referring again to FIG. 3, it will be seen that the torroidal chamber defined by annular depressions 24 and 26 is entirely filled with fusible alloy and, thus, the alloy defines a ring within the chamber. The force of spring 18 is therefore distributed throughout the entire circumference of staff 16 and bore 14. Accordingly, the pressure or stress on the fusible material is insignificant.

Further contributing to the secure retention of staff 16 in the bore against the force of spring 18 is outwardly converging sidewall portion 30 of annular depression 24 which serves to resist the torsional moment imparted by the force of spring 18 on fusible material 28 through the surface of annular depression 26. It will be noted, moreover, that bore 14 is provided with a shoulder 32 for engaging the inner end of spring 18 and that staff 16 is provided with an enlarged diameter portion 34 forming a collar for engaging the outer end of the spring so that stafi 16 is biased outwardly of shell 12 by the spring. An end cap or bushing 36 is forcefitted into the upper end of bore 14 so as to limit slidable movement and prevent escape of staff 16 when fusible alloy 28 yields the collar abutting against end cap 36 and inherently sealing the open end of the bore when the staff is extended.

It will be noted in FIG. 1 that staff 16 is symmetrical with respect to enlarged diameter portion 34. That is to say, the outer end is provided with a convex portion 22' and an annular depression 26 which are identical in all respects to similar elements on the other end of the staff. The purpose of the symmetry of staff 16 in this respect is to promote automated or machine assembly of the device and to eliminate any necessity for polarizing or aligning staff 16 on insertion into the bore 14.

When the device is assembled with metal alloy 28, staff 16, and end cap 36 in place in bore 14 of sleeve 12, the device can be cocked or loaded by immersing the entire sleeve in an ambient temperature environment having a temperature level in excess of the temperature of fusion of fusible alloy 28. On attainment of such condition, staff 16 is moved inwardly so that convex portion 22 seats in concave portion 20 and forces the molten fusible alloy into the torroidal chamber defined between annular depressions 24 and 26. Retention of the staff in such position until fusible alloy 28 cools and solidifies readies the device for use. After the device has been triggered, it can readily be reset by the preceding procedure and can be reused many times.

Referring to FIGS. 4-6, a modification of the present device is shown. Bore 14 of shell 12 has formed on the bottom thereof a generally wedge-shaped protuberance 38 extending generally diametrally of the bore. The

inner end of staff 16 has a diametrally extending slot 40 which bifurcates the inner end of the staff and which terminates at the inner end of the staff in an excised portion 42 that is formed complementarily with wedgeshaped protuberance 38. The remainder of the inner end of the staff is complementarily formed with wedgeshaped protuberance 38 and the concavities on either side thereof so that on movement of staff 16 inwardly of bore 14, fusible material 44 will be expelled from the bottom of the bore up into slot 40. As can best be seen in FIG. 5, such action will move the fusible material up into slot 40 wherein, after the material has solidified, it will hold the furcations of staff 16 apart from one another. The outer surface of staff 16 is formed with a pair of ridges 46 which are received in opposed complementary depressions 48 in the wall of bore 14. The depressions have an outwardly converging surface portion 50, which in cooperation with the force of spring 18, biases the furcations of staff 16 inwardly. It will be seen that so long as fusible metal 44 is within slot 40, such inward force is resisted and stafi 16 is retained in bore 14.

The embodiment of the present invention shown in FIGS. 1-3 responds at the temperature at which fusible material crystallizes, that is, a temperature lower than the fusion temperature of the metal anda temperature that is very constant throughout various samples of the same alloy. By way of contrast, the embodiment depicted in FIGS. 4-6 yields at the temperature fusion of the material since the material is subjected to compressive forces only.

Thus, it will be seen that the present invention provides a temperature-responsive device that can be produced substantially automatically and inexpensively, that is reusable, and that distributes forces over a broad area of the fusible material thereby reducing the pressure on the fusible material to a minimum. The last-mentioned feature of the present invention virtually eliminates false triggering that occurs in certain prior art structures of this type as a result of fatigue of the fusible material.

Although two embodiments of the invention have been shown and described, it will be apparent that other adaptations and modifications can be made without departing from the true spirit and scope of the invention.

lclaim:

1. In a temperature-responsive device of the type having a bored shell, a staff slidable in said shell, and means for biasing the staff outwardly of the shell, the improvement comprising the inner axial end of said staff and bottom of said bore being formed with complementally nestable surface portions so that urging said staff inwardly of said bore to the bottom thereof substantially totally expels flowable material axially outwardly of the space between said staff end and said bore bottom, means in fluid communication with said space between said complementally nestable surface portions for defining a chamber filling of which affords a lock against sliding movement of said staff relative said sleeve bore, and a quantity of solidified fusible material in said chamber for inhibiting axial movement of said staff relative said bore.

2. In a temperature-responsive device of the type having a bored shell, a staff slidable in said shell, and means for biasing the staff outwardly of the shell, the improvement comprising a generally wedge-shaped protuberance formed on the inner end of said bore and extending generally diametrally thereof, an excised portion complementary with said protuberance formed on the inner end of said staff, a slot formed in said staff in communication with said excised portion and extending generally diametrally of said staff, at least one depression formed in said bore, a ridge complementary with said depression formed on said staff so that on engagement between said excised portion on'said protuberance said ridge is urged into said depression, and a quantity of fusible metal having a preselected yield temperature in said bore, whereby on raising the ambient temperature of said fusible metal and urging said staff inwardly of said bore, fused metal is forced into said slot and on cooling to below the yield temperature, the metal in said slot solidifies to retain said ridge in said depression, thereby retaining the staff in the bore against the force of the biasing means.

3. A signaling device adapted to be inserted into an article to indicate the attainment of a predetermined iii hb ti s ifi g d ii riifi g ziii ardally extensive cavity closed at one end and open at the other end, said cavity having a groove formed therein and extending therearound and said housing being fluid tight except for the open end of said cavity and formed of a thermally conductive imperforate material;

. an axially extensive indicator rod received in said cavity for axial slidable movement relative to said housing between retracted and extended positions, said rod having a groove formed therein and extending therearound, said groove being located so as to be directly opposite the groove in said cavity when said rod is in the retracted position;

0. resilient means interposed between said rod and housing adapted to urge said rod to the extended position;

. a ring fusible at said predetermined temperature disposed in said grooves to normally maintain said rod in the retracted position and restrain said resilient means, said ring upon fusion being adapted to release said rod for extension by said resilient means; and,

e. means to limit slidable movement of said rod relative to said housing and sealingly close said cavity when said rod is in the extended position, said means comprising:

1. a collar fixed to and extending around said rod intermediate the ends thereof, said collar being slidable within said cavity upon movement of said rod between extended and retracted positions; and,

2. a bushing fixedly received in the open end of said cavity, said bushing being adapted to slidably receive said rod upon movement thereof between the retracted and extended positions and to sealingly abut against said collar when the rod is in the extended position.

. A device according to claim 3, wherein:

said resilient means comprises a coil spring disposed around said rod and within said cavity between said collar and the closed end of said caviy;

b. the ends of said spring abut against opposed surfaces on said collar and cavity when the rod is in both the retracted and extended positions.

FUSIBLE TEMPERATURE RESPONSIVE TRIGGER DEVICE This invention relates to a temperature-responsive triggering device wherein a fusible metal locking body retains. two relatively moveable parts of the device in fixed relation against a biasing force until a preselected temperature is attained.

Of the many applications of the present invention, a temperature indicating device for apprising a chef of the cooked condition of viands, as disclosed in my copending application Ser. No. 352,391 and in U. S. Pat. No. 3,140,611, is cited here byway of example. A myriad of uses for the invention will occur to those skilled in the art, for example, in fire alarm systems and the like.

Prior art temperature-responsive devices employing a fusible alloy with which I am familiar require installation of a new fusible link or body when the device is reset after having been subjected to a temperature in excess of the yield temperature of the fusible alloy. Such replacement is not only expensive but is also troublesome in that such fusible metal bodies or links are frequentlyof very small size and mounted in virtually inaccessible portions of devices of the type here under discussion. Another disadvantage in such prior art devices is that the fusible metal is under constant stress, usually as a result of spring tension or like biasing element, and is subject to false indications resulting from fatigue of the fusible metal body. Attempts to strengthen the fusible link or locking body by enlarging it adversely affects the temperature sensitivity of the device; enlargement is impossible in compact devices such as those used in preparing viands.

For illustration, the present invention is hereinafter described in connection with a temperature-responsive device of the type described more fully in the U. S. Pat. 3,140,61 1 wherein an outer shell having a pointed end is provided and which shell is inserted into a fowl, roast, or like viand prior to placement into an oven. Such shell is bored to slidably receive a staff therein, a spring being provided for biasing the staff outwardly of the bore. A fusible locking body is provided within the bore for retaining the staff therein and against the force of the spring until a preselected temperature has been reached within the viand. Specific exemplary roasting conditions are disclosed in my copending patent application cited above. When a preselected temperature occurs adjacent the fusible element, the latter yields and permits the spring to move the staff outwardly of the shell, thereby providing a visual indication of the arrival of the preselected temperature. Although the prior art fusible links or bodies have been generally successful, the structure of the present invention provides a marked improvement. 1

In the present invention, the bottom of the bore and the inner end of the staff are formed with complementary surfaces so that when the staff is urged inwardly of the bore virtually no space exists between the longitudinal ends of the staff and bore. Adjacent the complementary portions, the staff and the bore are each formed with a mutually confronting annular depression or groove. Consequently, when a body of fusible metal is placed in the bore and is heated to a molten state, movement of the staff into the bore forces the molten metal out of the space between the staff and bore and into the generally torroidal chamber formed by the two annular depressions. The staff is there retained until the fusible metal is solidified by cooling at which point a secure, temperature-sensitive lock is afforded between the staff and the shell.

A feature and advantage of the present invention is that substantially all of the fusible metal contributes to withstanding the biasing force tending to move the staff relative to the bore. Accordingly, the unit stress on the material is reduced as a consequence of which false indications are eliminated and the amount of fusible metal needed is minimized.

A further feature and advantage of the device of this invention is that after the device triggers at the preselected temperature, the device can be reset merely by urging the staff inwardly of the bore and reducing the ambient temperature below the temperature of fusion of the fusible metal. By way of contrast, attention is respectfully invited to the patent cited hereinabove wherein a transversely extending pin has ends protruding for locking the staff in fixed relation to the bore and wherein on attainment of the yield temperature the ends of the pins are sheared off. Such prior art device can be reset only by disassembly and insertion of a new fusible pin.

Another feature and advantage of this invention resides in forming the annular groove in the sleeve bore with an outwardly converging surface portion so that the force imparted to the fusible body by the spring or like biasing means tends to lock the staff in the bore more firmly. Such outwardly converging wall portion imparts to the fusible body a torsional moment which distributes shear stresses throughout the fusible body rather than along a cylindric plane of the boundary between the staff and the shell bore. Accordingly, false temperature indications are further reduced or eliminated.

Still another feature and advantage of the present invention arises from a modification of the device wherein the staff is provided with a ridge on the surface thereof for entry into the annular depression in the sleeve bore. Such modified staff further includes at least one diametrally extending slot into which fusible metal is forced to urge the ridge into engagement with annular depression in the sleeve bore. The inner end of the staff and bore are formed with complementary surfaces so that on urging the staff inwardly of the bore when the metal is at the temperature of fusion, the molten metal will be forced into the slot and there retained after cooling to a temperature below the temperature fusion of the metal. When the temperature is again raised to the fusion temperatures of fusible metal, the stafi is freed to outward movement in response to the spring bias.

The foregoing as well as other objects, features and advantages will be more apparent after referring to the following specification and accompanying drawings in which:

FIG. 1 is a cross-sectional view of a temperatureresponsive device embodying the present invention;

FIG. 2 is an enlarged detailed view of a portion of FIG. 1;

FIG. 3 is a view similar to FIG. 2 wherein the temperature-responsive trigger is in locked condition;

FIG. 4 is a detailed view of a modification of the present invention;

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,682 130 Dated August 8, 1972 William D. Jeffers It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

In the identification sheet: item [73] should identify the assignee as DUN-RITE MANUFACTURING CORP. Fresno, Calif. item [56] should show the inventor of UNITED STATES PATENT 3,140,611 as --Kliewer rather than "Kliwer" and the last mentioned attorney should be -John K. Uilkemarather than "John K. Wilkinson.

Signed and sealed this 3rd day of April 1975.

(SEAL) Attest:

EDWARD M.PLETCH ER,JR. ROBERT GOTTSCHALKv Attesting Officer Commissioner of Patents 

1. In a temperature-responsive device of the type having a bored shell, a staff slidable in said shell, and means for biasing the staff outwardly of the shell, the improvement comprising the inner axial end of said stAff and bottom of said bore being formed with complementally nestable surface portions so that urging said staff inwardly of said bore to the bottom thereof substantially totally expels flowable material axially outwardly of the space between said staff end and said bore bottom, means in fluid communication with said space between said complementally nestable surface portions for defining a chamber filling of which affords a lock against sliding movement of said staff relative said sleeve bore, and a quantity of solidified fusible material in said chamber for inhibiting axial movement of said staff relative said bore.
 2. In a temperature-responsive device of the type having a bored shell, a staff slidable in said shell, and means for biasing the staff outwardly of the shell, the improvement comprising a generally wedge-shaped protuberance formed on the inner end of said bore and extending generally diametrally thereof, an excised portion complementary with said protuberance formed on the inner end of said staff, a slot formed in said staff in communication with said excised portion and extending generally diametrally of said staff, at least one depression formed in said bore, a ridge complementary with said depression formed on said staff so that on engagement between said excised portion on said protuberance said ridge is urged into said depression, and a quantity of fusible metal having a preselected yield temperature in said bore, whereby on raising the ambient temperature of said fusible metal and urging said staff inwardly of said bore, fused metal is forced into said slot and on cooling to below the yield temperature, the metal in said slot solidifies to retain said ridge in said depression, thereby retaining the staff in the bore against the force of the biasing means.
 2. a bushing fixedly received in the open end of said cavity, said bushing being adapted to slidably receive said rod upon movement thereof between the retracted and extended positions and to sealingly abut against said collar when the rod is in the extended position.
 3. A signaling device adapted to be inserted into an article to indicate the attainment of a predetermined internal temperature, comprising: a. tubular housing defining an axially extensive cavity closed at one end and open at the other end, said cavity having a groove formed therein and extending therearound and said housing being fluid tight except for the open end of said cavity and formed of a thermally conductive imperforate material; b. an axially extensive indicator rod received in said cavity for axial slidable movement relative to said housing between retracted and extended positions, said rod having a groove formed therein and extending therearound, said groove being located so as to be directly opposite the groove in said cavity when said rod is in the retracted position; c. resilient means interposed between said rod and housing adapted to urge said rod to the extended position; d. a ring fusible at said predetermined temperature disposed in said grooves to normally maintain said rod in the retracted position and restrain said resilient means, said ring upon fusion being adapted to release said rod for extension by said resilient means; and, e. means to limit slidable movement of said rod relative to said housing and sealingly close said cavity when said rod is in the extended position, said means comprising:
 4. A device according to claim 3, wherein: a. said resilient means comprises a coil spring disposed around said rod and within said cavity between said collar and the closed end of said cavity; and, b. the ends of said spring abut against opposed surfaces on said collar and cavity when the rod is in both the retracted and extended positions. 